Stern-on mooring boat lift

ABSTRACT

In a lift for mooring a boat stern-on, a pair of horizontally spaced guide members is fixed to the sea wall. A frame is fixed to a pair of substantially parallel hydro-pneumatic buoyancy tanks to provide a flotation platform for supporting the hull of the boat. The stern end of each of the tanks is connected to the guide members. The guide members limit movement of the platform away from the sea wall and along the sea wall but permit vertical reciprocation of the stern ends of the lift tanks in unison and restrict the lift from listing during operation.

BACKGROUND OF THE INVENTION

[0001] This invention relates generally to water craft and moreparticularly concerns lifts for boats.

[0002] Boat lifts are presently available for side-mooring and bowmooring boats to a sea wall or dock. While stern-mooring of a boat on alift would be very convenient for boarding and disembarkment,stern-moored boat lifts are not presently known. The motion andpositioning of side and bow mooring lifts during operation prevent theiruse for stern mooring.

[0003] Side mooring lifts cannot be used for stern mooring becauseduring operation, their motion is controlled by guides connecting thelift to the sea wall or dock both fore and aft. As the lift is operated,the bow and stern do not move together. During lowering, air isinitially evacuated from one end of the lift tanks as water enters theother end, causing the lift to displace angularly downwardly about theair outlet end. As the water volume in the tank increases, the airoutlet end also lowers and the tank returns to a level condition. Theprocess is reversed when the lift is raised. To accommodate this angularmotion, the guide components connecting the lift to the sea wall or dockare constructed to function independently so that the portion of thelift connected to the sea wall or dock is free to reciprocateindependently. A stern-moored lift cannot be permitted to displaceangularly or list on its guide components. The guide components mustwork in unison with each other to maintain the lift in a laterally levelcondition while the bow and stern each displace angularly.

[0004] Bow mooring lifts cannot be used for stern mooring either. Theyare generally pivoted at the sea wall or dock so that the bow endremains elevated while the stern end is lowered to receive the boat, bowfirst. Consequently, if bow mooring lifts were used for stern mooring,the aft portion of the boat, and especially the propeller, would strikethe bow end of the lift.

[0005] It is, therefore, an object of this invention to provide a boatlift for stern mooring boats to sea walls and docks. Another object ofthis invention is to provide a boat lift having stern mounted guides forcontrolling the operational motion of the lift. A further object of thisinvention is to provide a boat lift having guide components which limitlateral movement of the lift in relation to the sea wall or dock. Yetanother object of this invention is to provide a boat lift having guidecomponents which, when stern mounted to the sea wall or dock, allow thestern to move freely vertically in relation to the sea wall or dock. Itis also an object of this invention to provide a boat lift having sternmounted guide components which function to allow vertical reciprocationof the stern portions of the lift tanks in unison with each other.

SUMMARY OF THE INVENTION

[0006] In accordance with the invention, a lift for mooring a boatstern-on to a sea wall or dock is provided. A pair of horizontallyspaced guide members fixed to the sea wall extend from the sea wall to avertical plane parallel to the sea wall. A pair of substantiallyparallel hydro-pneumatic buoyancy tanks are symmetrically spaced from avertical plane which is perpendicular to the parallel plane and extendssubstantially midway between the guide members. A frame is fixed to thetanks to provide a flotation platform for supporting the hull of theboat. The keel of the boat is received substantially aligned with theperpendicular plane and the stern of the boat is received at the sternend of the platform near the sea wall. Each of the tanks is connected tothe guide members. The guide members limit movement of the platform awayfrom the parallel plane or sea wall and away from the perpendicularplane or laterally along the sea wall. The guide members also operate inunison to restrict the lift from listing during operation.

[0007] In one preferred embodiment, a pair of horizontally spacedvertical tracks are fixed to the sea wall proximate their upper ends.They extend from the sea wall to a vertical plane parallel to the seawall. A pair of slides are each fixed at one end to the stern ends ofeach of the tanks. They each engage and ride at their other end on thetracks. The slides limit movement of the platform away from the parallelplane or sea wall and away from the perpendicular plane or laterallyalong the sea wall while permitting the stern of the platform toreciprocate in unison vertically along the tracks. Preferably, theslides have pivoting linkages facilitating vertical displacement of thetanks relative to the guide members and restricting lateral displacementof the tanks relative to the guide members. The pivoting linkages eachpreferably have a clevis fixed to the slide, a bracket fixed to the tankand a link pivotally connected at one end to the clevis and at the otherend to he bracket. The links are formed from elastomeric material. Thetracks are I-beams with their webs disposed in the vertical plane. Theslides are members of C-shaped cross-section engaged on flanges of theI-beams. An anchor may optionally be disposed on the sea floor forwardof the tanks and substantially aligned on the perpendicular plane. Aline connected between the anchor and the bow portion of the platform atsubstantially the mid-point between the tanks limits movement of the bowend of the platform away from the perpendicular plane or laterally alongthe sea wall.

[0008] In another preferred embodiment, a pair of horizontally spacedrings fixed to the sea wall extend from the sea wall to the verticalplane parallel to the sea wall. An anchor is disposed on the sea floorforward of the tanks with a line connecting the anchor to the bowportion of the platform. One pair of lines is connected between each ofthe rings and the bow end of its corresponding tank. A second pair oflines may also be connected between each of the rings and the stern endof its opposite tank or between each of the rings and the opposite sidesof the stern of the boat. The anchor line and the first pair of lineslimit movement of the platform toward and away from the parallel planeor sea wall and laterally along the sea wall while permitting the sternof the platform to reciprocate vertically in unison along the tracks.The second pair of lines assist in restricting lateral movement of theplatform along the sea wall when the lift is not in operation but mustbe cast off before operation of the lift.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Other objects and advantages of the invention will becomeapparent upon reading the following detailed description and uponreference to the drawings in which:

[0010]FIG. 1 is a top plan view of a preferred embodiment of thestern-on lift with a boat on the lift;

[0011]FIG. 2 is a front elevation view of the lift and boat of FIG. 1 inboth lowered and raised conditions;

[0012]FIG. 3 is a side elevation view of the lift of FIG. 1 in theraised condition;

[0013]FIG. 4 is a perspective view of a preferred embodiment of guidemember of the lift of FIG. 1;

[0014]FIG. 5 is a side elevation view of the guide member of FIG. 4;

[0015]FIG. 6 is a top plan view of the guide member of FIG. 4;

[0016]FIG. 7 is a top plan view of another preferred embodiment of thestern-on lift with a boat on the lift;

[0017]FIG. 8 is a side elevation view of the lift and boat of FIG. 7;and

[0018]FIG. 9 is a front elevation view of the lift and boat of FIG. 7.

[0019] While the invention will be described in connection with apreferred embodiment, it will be understood that it is not intended tolimit the invention to that embodiment. On the contrary, it is intendedto cover all alternatives, modifications and equivalents as may beincluded within the spirit and scope of the invention as defined by theappended claims.

DETAILED DESCRIPTION

[0020] Turning first to FIGS. 1-3, a lift L for stern-mooring a boat Bto a sea wall S is illustrated. As seen in FIG. 2, when the lift L is inits fully lowered condition, the lift L is substantially level and theboat B floats freely on the water W. When the lift is in its fullyraised condition, the lift L is substantially level and the boat B issupported by the lift L entirely out of the water W. In the operation ofthe lift L, to lower the lift L, water is admitted to the stern end ofthe hydropneumatic tanks as air is evacuated from the bow end of thetanks. As seen in FIG. 3, the lift L is lowered stern end first whilethe bow end remains elevated. The bow end then sinks until the lift L issubstantially level.

[0021] The lift flotation platform consists of a pair of substantiallyparallel hydropneumatic buoyancy tanks 11 and 13 which are symmetricallyspaced from a vertical plane 15 which is perpendicular to anothervertical plane 17 which is in turn parallel to the sea wall S. As apoint of reference, the perpendicular plane 15 extends substantiallymidway between a pair of guide members 19 and 21 which are horizontallyspaced apart and fixed to the sea wall S and extend from the sea wall Sto the parallel vertical plane 17. A frame 23 fixed to the tanks 11 and13 supports the hull of the boat B with the keel of the boat Bsubstantially aligned with the perpendicular plane 15 and the stern ofthe boat B at the stern end of the lift L. A pair of connectors 25 and27 connect the stern end of each of the tanks 11 and 13 to theirrespective guide members 19 and 21 to limit movement of the lift L awayfrom the parallel plane 17 or sea wall S and to limit movement of thelift L away from the perpendicular plane 15 or laterally in relation tothe sea wall S. The connectors 25 and 27 also permit the stern ends ofthe tanks 11 and 13 to move vertically in unison relative to guidemembers 19 and 21. A pair of floats 29 and 31 fixed to and extendingabove and parallel to the tanks 11 and 13 limit the depth to which thelift L is lowered. An anchor 33 disposed on the sea floor forward of thetanks 11 and 13 and substantially aligned on the vertical plane 15 isconnected by a line 35 to the bow portion of the lift L at substantiallya midpoint between the tanks 11 and 13 so as to assist in restrictingmovement of the lift L toward the parallel plane 17 or sea wall S andaway from the perpendicular plane 15 or along the sea wall S.

[0022] Turning to FIGS. 4, 5 and 6, the guide members 19 and 21 and theconnectors 25 and 27 are shown in greater detail. In the preferredembodiment shown in FIGS. 4, 5 and 6, the guide members 19 and 21consist of I-beams having their webs 37 parallel to the vertical plane15 and their front flanges 39 lying in the parallel plane 17. The rearflanges 41 are fastened proximate their upper ends by brackets 43 to thesea wall S. The lower ends of the guide members 19 and 21 are sunk intothe sea floor. A slide 45 is engaged on and rides on the front flange39. As shown, the preferred slide is a vertically elongated member ofC-shaped cross section having its back portion engaged on the flange 39and its forward portion extending away from the flange 39. The slides 45have pivoting linkages including a clevis 47 fixed to the slide 45, abracket 49 fixed to the stern end of the tank 11 or 13 and a link 51pivotally connected at pins 53 and 55 to the clevis 47 and the bracket49, respectively. Most preferably, the link 51 is elastomeric. Theslides 45 and their linkages limit movement of the flotation platformaway from the parallel plane 17 or sea wall S and away from the verticalperpendicular plane 15 while permitting the stern ends of the tanks toreciprocate vertically in unison along the flanges 39 of the guidemembers 19 and 21. The pivoting action and elastomeric quality of thelink 51 allow the bow and stern ends of the lift to reciprocateindependently and absorb the stresses which occur during operation ofthe lift L while facilitating the vertical reciprocation of the tanks inunison. Alternatively, the I-beam may be fixed to the float and theslides 45 fixed to the dock or sea wall and still be in keeping with theprinciples of the invention.

[0023] Turning now to FIGS. 7-9, an alternative embodiment of thestern-on lift L is illustrated. The guides 19 and 21 consist ofhorizontally spaced rings 57 and 59 fixed to the sea wall S andextending from the sea wall S to the vertical plane 61 parallel to thesea wall S. The anchor 63 is disposed on the sea floor forward of thetanks 11 and 13 substantially aligned on the perpendicular plane 65extending through the midpoint 67 between the tanks 11 and 13 and therings 57 and 59. A line 69 connects the anchor 63 to the bow portion ofthe platform at substantially the midpoint 67 and limits movement of theplatform toward the parallel plane 61 or sea wall S and away from theperpendicular plane 65 or laterally in relation to the sea wall S. Apair of lines 71 and 73 are connected between each of the rings 57 and59 and the bow end of corresponding ones of the tanks 11 and 13. The bowlines 71 and 73 limit movement of the platform away from the parallelplane 61 or dock S and away from the perpendicular plane 15 or along thesea wall S while permitting the stern ends of the tanks 11 and 13 toreciprocate vertically in unison along the sea wall S or parallel plane61. A second pair of lines 75 and 77 connecting the rings and the sternends of opposite ones of the tanks 11 and 13 or of opposite sides of theboat B may be used to limit movement of the stern end of the platformaway from the parallel plane 61 or sea wall S and away from theperpendicular plane 65 or laterally along the sea wall S but only whenthe lift is not in operation. During operation of the lift the secondpair of lines 75 and 77 must be cast off.

[0024] In operation, with a boat B elevated out of the water W by thelift L as shown in FIGS. 2 and 8, as water is introduced into the sternend of the tanks 11 and 13 and air is evacuated from the front end ofthe tanks 11 and 13, the stern ends of the tanks 11 and 13 will first belowered in unison into the water W. In the track embodiment of FIGS. 1through 6, the tracks or flanges 39 and slides 45 restrict lateralmotion of the tanks 11 and 13 and longitudinal motion of the tanks 11and 13 while permitting the tanks 11 and 13 to reciprocate in unisonvertically. The pivoting elastomeric links 51 allow the stern ends ofthe tanks 11 and 13 to reciprocate independently of the bow ends of thetanks 11 and 13 to absorb external stresses applied to the liftcomponents. In the ring embodiment of FIGS. 7-9, the stern lines 75 and77 will have been cast off before beginning operation of the lift. Thebow lines 71 and 73 limit lateral and forward motion of the tanks whilethe line 69 connected to the anchor 63 limits rearward motion of thetanks. The bow lines 71 and 73, however, permit vertical motion of thestern ends of tanks 11 and 13 in unison with respect to the parallelplane 61 or sea wall S. In either embodiment, when the stern ends of thetanks 11 and 13 are fully lowered to the level limited by the floats 29and 31 on the sides of the lift L, the bow portions of the tanks 11 and13 also fill with water, causing the lift L to come to a levelcondition, as is best seen in FIG. 3. In this lowered condition, theboat B is supported solely by the water W and is ready to be launched.In redocking the boat B, the boat B is backed onto the lift L in itsfully lowered condition. The hydropneumatic process is then reversed,causing the bow end of the lift L to be raised initially, followed bythe stern end of the lift L until the hull of the boat B is entirely outof the water W.

[0025] Thus, it is apparent that there has been provided, in accordancewith the invention, a stern-on boat lift that fully satisfies theobjects, aims and advantages set forth above. While the invention hasbeen described in conjunction with a specific embodiment thereof, it isevident that many alternatives, modifications and variations will beapparent to those skilled in the art and in light of the foregoingdescription. Accordingly, it is intended to embrace all suchalternatives, modifications and variations as fall within the spirit ofthe appended claims.

What is claimed is:
 1. A lift for mooring a boat stern-on to a sea wallcomprising: a pair of horizontally spaced guide members fixed to the seawall and extending from the sea wall to a vertical plane parallel to thesea wall; a flotation platform having a pair of substantially parallelhydro-pneumatic buoyancy tanks symmetrically spaced from a verticalplane perpendicular to said parallel plane and extending substantiallymidway between said guide members and a frame fixed to said tanks forsupporting a hull of the boat with a keel of the boat substantiallyaligned with said perpendicular plane and a stern of the boat at a sternend of said platform, said stern end of said platform being closer tosaid parallel plane; and means for connecting a stern end of each ofsaid tanks to said guide members for limiting movement of said platformaway from said parallel plane and away from said perpendicular plane andfor permitting said stern ends of said tanks to move vertically inunison.
 2. A lift according to claim 1, said connecting means comprisinga pivoting linkage permitting vertical angular displacement of saidtanks relative to said guide members and restricting lateraldisplacement of said tanks relative to said guide members.
 3. A liftaccording to claim 1 further comprising an anchor disposed on a floor ofthe sea forward of said tanks and substantially aligned on saidperpendicular plane; and a line connecting said anchor to a bow portionof said platform at substantially a mid-point between said tanks forlimiting movement of said platform toward said parallel plane and awayfrom said perpendicular plane.
 4. A lift according to claim 3, saidconnecting means comprising a pair of lines, one connected between eachof said guide members and a bow end of a corresponding one of saidtanks.
 5. A lift according to claim 4 further comprising a second pairof lines, one connected between each of said guide members and a sternend of an opposite one of said tanks.
 6. A lift for mooring a boatstern-on to a sea wall comprising: a pair of horizontally spacedvertical tracks fixed proximate an upper end thereof to the sea wall andextending from the sea wall to a vertical plane parallel to the seawall; a flotation platform having a pair of substantially parallelhydro-pneumatic buoyancy tanks symmetrically spaced from a verticalplane perpendicular to said parallel plane and extending substantiallymidway between said guide members and a frame fixed to said tanks forsupporting a hull of the boat with a keel of the boat substantiallyaligned with said perpendicular plane and a stern of the boat at a sternend of said platform, said stern end of said platform being closer tosaid parallel plane; and a pair of slides, one fixed at one end to astern end of each of said tanks and engaged and riding at another end onone of said tracks for limiting movement of said platform away from saidparallel plane and away from said perpendicular plane while permittingsaid stern ends of said tanks to reciprocate vertically in unison alongsaid tracks.
 7. A lift according to claim 6, each of said slides havinga pivoting linkage permitting angular displacement in a vertical planeof said tanks relative to said guide members and restricting lateraldisplacement of said tanks relative to said guide members.
 8. A liftaccording to claim 7, each said pivoting linkage comprising a clevisfixed to said slide, a bracket fixed to said tank and a link pivotallyconnected at one end to said clevis and at another end to said bracket.9. A lift according to claim 8, each said link being formed fromelastomeric material.
 10. A lift according to claim 6, said tracks beingI-beams having webs disposed along a common plane, said slides beingmembers of C-shaped cross-section slidably engaged on a flange of saidI-beams and having a pivoting linkage permitting angular displacement ina vertical plane of said tanks relative to said guide members andrestricting lateral displacement of said tanks relative to said guidemembers.
 11. A lift according to claim 6 further comprising an anchordisposed on a floor of the sea forward of said tanks and substantiallyaligned on said perpendicular plane; and a line connecting said anchorto a bow portion of said platform at substantially a mid-point betweensaid tanks for limiting movement of said platform toward said parallelplane and away from said perpendicular plane.
 12. A lift for mooring aboat stern-on to a sea wall comprising: a pair of horizontally spacedrings fixed to the sea wall and extending from the sea wall to avertical plane parallel to the sea wall; a flotation platform having apair of substantially parallel hydro-pneumatic buoyancy tankssymmetrically spaced from a vertical plane perpendicular to saidparallel plane and extending substantially midway between said guidemembers and a frame fixed to said tanks for supporting a hull of theboat with a keel of the boat substantially aligned with saidperpendicular plane and a stern of the boat at a stern end of saidplatform, said stern end of said platform being closer to said parallelplane; an anchor disposed on a floor of the sea forward of said tanksand substantially aligned on said perpendicular plane; a line connectingsaid anchor to a bow portion of said platform at substantially amid-point between said tanks for limiting movement of said platformtoward said parallel plane and away from said perpendicular plane; and apair of lines, one connected between each of said rings and a bow end ofa corresponding one of said tanks, for limiting movement of saidplatform away from said parallel plane and away from said perpendicularplane while permitting said stern ends of said tanks to reciprocatevertically in unison along said parallel plane.
 13. A lift according toclaim 12 further comprising a second pair of lines, one connectedbetween each of said rings and a stern end of an opposite one of saidtanks.